Freshwater ecosystems Kinds Characteristics Threats

Aquatic ecosystems Key distinction: salinity = salt content of the water Measured in parts per thousand (ppt) 1 gm of salt in 1000 gms water = 1 ppt FRESH usually < 0.5 ppt OCEANS average 35 ppt 0.5 to 17 ppt is called BRACKISH

Kinds of freshwater habitats Rivers, streams Flowing freshwater Source: where it starts Mouth: where it ends Lakes, ponds Wetlands

All freshwater ecosystems Just a fraction of the Earth’s water .01% = one one-hundredth of one percent Occupy less than 1 percent of the Earth’s surface

Rivers and streams More than 3.5 million miles of rivers and streams (including intermittent streams) Just the U.S.! More than 140 times around the Earth. www.noaa.gov/str-plan/images/river.gif The miles of rivers and streams in the United States is equivalent to more than 140 times the circumference of the earth – 140 trips around the equator. Identify some of the regional rivers and streams known by the students.

Rivers from start to finish Source = Headwaters Can be: Snowmelt Spring Even a lake Water is colder, clearer, more highly oxygenated Organisms include trout, mayflies Mouth: where the river ends Usually the ocean or another river, or lake River widens and slows, getting warmer, siltier. Middle is most diverse, lots of plants Near mouth, increased sediment limits light and plants, water is warmest

What are some of the differences? Trout stream, NW NJ Mississippi R. Greenville, MS

Mouth Mississippi River delta

Lakes and ponds What’s the difference? Ponds typically smaller May be seasonal—that is, dry up part of the year Lakes exist hundreds or thousands of years But, even lakes can fill in or dry up

Parts of a lake

Parts of a lake Littoral zone: near shore Nutrient rich, lots of plant and animal life Warm Limnetic zone: near surface, open water Lots of light Lots of plankton Profundal zone: deeper, little light Benthic zone: the bottom, little light, low oxygen

Eutrophication If nutrients increase too much in a lake, pond, or ocean, excessive plant growth results Phosphorus Nitrogen NOT GOOD: why? As plants decay, decomposing bacteria use oxygen dissolved in the lake to do their jobs. Dissolved oxygen goes down

Wetlands CA OR AK

Wetlands: what are they? For regulatory purposes under the Clean Water Act, the term wetlands means "those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas."

Wetlands May be fresh or brackish Freshwater types include: Marsh Swamp Bog Fen

Marsh Most common freshwater wetland in U.S. Occur along streams or in depressions Characterized by organic, wet soils and non-woody (i.e., no trees) vegetation.

Swamp Wetland dominated by woody plants Common in SE U.S.

New Jersey wetlands About 916,000 acres, or 19% of New Jersey, is wetlands, which seems like a lot; but the bad news is that about 40% of the original 1,500,000 acres has been lost to dredging and filling, dams, farming, development and highways.

NJ wetlands

What good are wetlands? Reduce flooding by acting like sponges

What good are wetlands? Help clean water by acting like a filter The plants and slow water flow in a wetland help remove pollutants, leaving water cleaner downstream in a lake or river. Too much pollution can leave a wetland toxic to visiting animals, such as many birds.

What good are wetlands? Protect shorelines from erosion Erosion in this case came from grazing animals